Electric filter



Nov. 12, 1940.

R. OTTO 2,221,105

ELECTRIC FILTER Filed May 6, 1959' L L C -l-lifm-o H62 fmr 3:/3

Myne

*V//l//l/l/l//l/l/I//l/l/l//l 8 RUDOLF OTTO ATTORNEY Patented Nov. 12, 1940 UNITED STATES ELECTRIC FILTER RudolfOtto, Berlin-Siemensstadt, Germany, as-

signor to Fides Gesellschaft fr die Verwaltung und Verwertung von gewerblichen Schutzrechten mit beschrnkter Haftung, Berlin, Germany, a corporation of Germany Application May 6, 1939, Serial No. 272,082

In Germany May 7, 1938 v 3 Claims.

The invention relates .to electric iiltersv con taining parallel condensers, more especially to coil connections and is concerned with the construction of the shielding of the lter elements which is especially important in the case of very high frequencies. The question of shielding often involving diiculties is solved in a simple way by the arrangement according to the invention.

In accordance with the invention one of the series branches, namely the ground line is designed as a shield which surrounds the filter elements and certain layers namely the ground layers of all parallel condensers, or of a part of the parallel condensers are formed by cross Walls of the shield while the other layers consist of foils or disks which are connected with connection lines or connecting conductors of the other series branch which lines are extended through the cross walls while insulated therefrom. The construction according to the invention aiords a complete lter action since on account of the special arrangement of the shield in connection with 4the design of the parallel condensers a practically gap-less shielding of the coils against eX- terior elds and against one another is accomplished. The particular construction of the parallel condensers provides an especially short length of the parallel branches and a negligible inductance of the condensers.

The invention will be better understood by reference to the accompanying drawing wherein Fig. l shows schematically the electrical lter system according to the invention; Fig. 2 shows the lstructural arrangement of the filter, Figs. 3, 4 and 5 disclose modifications of the condenser elements for use with the invention, and Fig. 6 is an alternative form of shield. A principal scheme of a coil line constructed in accordance with the invention is shown in Figure 1. The

coil connection provided with the input terminals l, 2 and output terminals 3, 4 contains in a series branch the coils L1 and L2 and in the parallel branches the condensers C1 to C3. The one series branch, namely the ground line, is designed as a shield surrounding the filter elements and has more particularly the shape of a cylinder which together with the ground layer of the through lead condensers preferably forming a round disk, establishes completely shielded spaces.

A inode of construction of a coil connection constructed in accordance with the invention is shown by way of example in Figure 2. The shielding of the lter elements forming the one series branch is represented by the cylinder ring 5 and the round disks 6. The round disks E forming the ground layer of .the conden'sersl C1 to C3 have bolts passed therethrough which are insulated from said disks and which serve atthe same time for the clamping together of the condenser layers. f

Figure 3 shows a part of a cross Wall together With the condenser thus formed. The cross wall forming the one layer b has in the center thereof an insulating disk c through which the bolt e is passed. The other layers of the condenser are formed by the disks a arranged on each side and which are joined with the bolts. The dielectric is formed by mica disks d. The mica disks preferably' are provided with conducting layers at the places where they come in Contact with the layers, these conducting layers consisting preferably of silver. Each side of the bolts has a respective soldering ear. The desired capacity can be obtained by dimensioning the disks a accordingly. In order to increase the capacity a mod-e of con-struction of the condenser according to Figure 4 may be advisable. In this condenser there is provided further foils b and a separated by dielectrics and arranged between .the cross Wall b and one, or both disks a. The foils b are extended on one side or on both sides beyond the mica disks or the like and connected with the cross walls for instance through spot welding. The layers a are placed directly upon the bolts e so that a very short path and zero inductance is obtained also in this mode of construction. In order to obtain a favorable contact it may be of advantage to provide conducting disks f between the disks a and the disks a such as shown in Figure 5. Instead of using mica as the dielectric also other high quality dielectric materials may be employed more especially polystyrol or ceramic insulating materials,

The coils L1 and L2 shown in the Figure 1 in the form of helical coils are centrally mounted by insulating disks l. The connection ends of the coils are connected with the connection ears of the through bolts in that they are passed through openings of the'insulating disks. The plates and shields are simply placed upon one another in this mode of construction and have openings at the borders thereof so that the plates and shields enter each other. They are held together by means of through-going bolts 8 Which at the same time maintain the insulating disks 1 in position by means of spacers 9. It may be of advantage to provide the cross plates with ears protruding from the sides and to arrange the bolts outside the shielded inner spaces. It will be advantageous to screw together the plates forming the cross walls and the shields formed more particularly by cylindrical rings, or to hold these parts together by means of nuts such as shown in Figure 6. The shielding rings 5 and the plates 6 are provided preferably with a covering having favorable conduction, more especially With a silver covering. In this case they may also be made of insulating material for instance of the known pressed materials. In this case care is to be taken that the metallic covering having favorable conduction adheres favorably at all places and that an objectionable contact is assured.

What is claimed is:

1. An electric filter comprising a metallic shield having metallic end members, said shield serving as a ground conductor for said lter, an inductance coil within said shield forming a series inductance for said filter, a metallic plate located on opposite sides of each metallic end member, each pair of said metallic plates and their interposed end member serving respectively as the high potential electrodes and the low potential electrode of a shunt-connected condenser for said lter, and an insulating member of mica located between each metallic plate and its associated metallic end member.

2. An electric iilter as defined in claim 1 wherein an insulating member is positioned within the shield and in spaced relation between the metallic end members, and means for supporting the series inductance from lsaid insulating member.

3. An electric lter comprising a cylindrical metallic shield which is adapted to serve as a ground conductor for said lter, alternate metallic and insulating disk members disposed in spaced parallel relation and tted within said shield, an inductance coil forming a series inductance for said lter supported from each insulating disk member, a metallic plate located on opposite sides of each metallic disk member, each pair of said metallic plates and their interposed metallic disk member serving respectively as the high potential electrodes and the low potential electrode of a shunt-connected condenser for said filter, and an insulating member of mica located between each metallic plate and its associated metallic disk member.

RUDOLF O'I'I'O. 

